The present invention relates to a plug-in connector capable of simply and appropriately connecting an electric wire with another electric wire only by inserting one end portion of the electric wire.
In a plug-in connector of this type, a contact element comprising a conductive plate for connecting electric wires with each other and a spring piece for urging an electric wire against the conductive plate is incorporated in a holder made of a heat-resistant insulating member. Wire connection can be easily performed by anybody only by peeling the coatings on the connection ends of electric wires to be connected and inserting the peeled portions through the insertion ports of the holder. Hence, plug-in connectors having various types of structures are conventionally known, e.g., one disclosed in Japanese Utility Model Publication Nos. 1-22228, 1-29738, and the like.
One of the requirements of this plug-in connector is a simple and assembly-facilitated pressure contact structure by means of the contact element of an electric wire. According to this structure, peeled portions of the electric wires as electric wire connection ends can be easily inserted in the holder, and after insertion, the peeled electric wire portions are reliably prevented from removal from the holder, so that the contact element and the electric wire peeled ends by pressure connection in this state can electrically contact each other with a high reliability.
More specifically, a conventional contact element comprising a conductive plate made of a copper member or the like and a leaf spring having a spring piece for urging the peeled electric wire portions against the conductive plate is used. Of the conventional contact elements, however, one which not only has a simple structure and can be assembled easily, but also can satisfy easy insertion of the peeled electric wire portions to be inserted, reliable electrical connection by ensuring a contact area and a contact pressure, and prevention of the inserted peeled electric wire portions from removal has not yet been proposed.
Especially, in most of the conventional contact elements, when the proximal end portion of a leaf spring is to be fixed on a conductive plate, a plurality of electric wire insertion holes are formed in one plate portion of an L-shaped bent conductive plate, a caulking piece is provided on the outer end of the conductive plate, and projecting portions provided to part of the caulking piece are caulked through holes formed in the leaf spring, thereby fixing the proximal end portion of the leaf spring on the conductive plate.
In the contact element employing caulking by means of the conductive plate and the leaf spring, electric wires are inserted in the electric wire insertion holes of the conductive plate, and the distal end portion of the leaf spring is urged against the inserted end sides of the electric wires, thereby electrically connecting the electric wires. At this time, when a force is applied in a direction to spread toward the electric wire receiving portions of the conductive plate and the distal end portion of the leaf spring, this force acts on the portions of the conductive plate having the electric wire insertion holes and the caulking portion of the leaf spring. Then, the portions of the conductive plate having the electric wire insertion holes and the caulking portion are deformed in a direction to move the distal end portion of the leaf spring away from the electric wires to decrease the pressure. As a result, the electrical conductivity is degraded.
Furthermore, in this conventional contact element, the following problem easily occurs. More specifically, the distal end side of the leaf spring can easily float from the conductive plate depending on the caulked state of the fixing portion fixed by caulking. Then, a gap between the leaf spring and the electric wire receiving portions of the conductive plate becomes larger than the diameter of the electric wires. Even when the electric wires are inserted, the leaf spring cannot firmly catch the electric wires. Removal of the electric wires may not be prevented.
An angle defined by the distal end side of the leaf spring, fixed by caulking to the conductive plate, and the conductive plate is significant in facilitating the plug-in operation of the electric wires and reliably preventing the electric wires from removal. More specifically, considering facilitation of wire insertion and reliable electrical connection of the electric wires, when the angle defined by the conductive plate and the leaf spring, both constituting the contact element, is set small, the function of the leaf spring that prevents the electric wires from removal is impaired. On the other hand, when the angle is set large in order to cause the leaf spring to firmly catch the electric wires and to reliably prevent the electric wires from removal, the electric wires cannot be easily inserted between the conductive plate and the leaf spring both constituting the electric wire contact element. In addition, a contact area cannot be ensured, thereby impairing electrical connection.
For this reason, the following structure has been conventionally proposed. According to this structure, a substantially U-shaped bent conductive plate and an almost V-shaped leaf spring incorporated inside the conductive plate are used. One plate portion of this leaf spring is arranged along the inner surface of one side portion of the conductive plate. The other plate portion of the leaf spring obliquely extends toward the other end portion thereof. When the peeled portions of the electric wires are inserted, the leaf spring is elastically deformed such that its bending angle is an acute angle. Then, the reactive force of the leaf spring urges the electric wire peel portions against the inner surface of the other side portion of the conductive plate.
With this structure, however, although the conductive plate and the leaf spring have a simple structure and can be assembled easily, there is a problem in obtaining the required clamped state of the electric wire peel portions. More specifically, when the peeled electric wire portions are inserted to flex the leaf spring at an acute angle, the reactive force of the leaf spring also acts on one bent side portion of the conductive plate to open the U-shaped conductive plate. Then, the clamped state of the peeled electric wire portions by means of the leaf spring cannot be maintained, and the reliability of the electrical connection of the electric wires cannot be ensured. In addition, the electric wires cannot be prevented from removal. Therefore, it is required to take a countermeasure that can solve all these problems.
Another one of the requirements of the plug-in connector described above is to recognize and discriminate whether the connecting ends of electric wires are reliably connected to each other by inserting them in the holder.
When the electric wires are not sufficiently inserted in the connector, not only the required reliability of connection between electric wires is impaired, but also defective contact can be easily caused, leading to a fire caused by heat generated by the defective contact.
For this reason, in order to prevent the erroneous insertion of the electric wires, for example, the following connector has already been proposed. According to this connector, an electric wire insertion identification piece that can be swung upon inserting an electric wire is provided to part of the holder of the connector. The motion of the identification piece is grasped visually or by the sense of touch.
However, if such an electric wire insertion identification piece or a window for externally confirming it is integrally formed in the holder or the like, a holder forming die tends to be complicated, resulting in an increase in cost. Therefore, it is also required to take some countermeasure to solve this problem.